Figure



March 10, 1964 w. A. GRAIG 3,124,096

WATERCRAFT Filed March 25, 1959 3 Sheets-Sheet i 50 IN VEN TOR. aft-B470I I149! 05/11/718 ,4. 689/6 Irina March 10, 1964 Filed March 25, 1959 W.A. GRAIG WATERCRAFT 3 Sheets-Sheet 2 IN VEN TOR.

IVA/05mm. 664/6 Mmh 10, 1964 w. A. GRAIG 3,124,096

WATERCRAFT Filed March 25, 1959 3 Sheets-Sheet 3 INVENTOR. WfllLf/flflel7. 669/6 prramvqyi United States Patent "cc 3,124,096 WATERCRAFTWaldernm A. Graig, 729 Grand Ave, Dayton 6, Ohio Filed Mar. 25, 1959,Ser. No. 801,793 13 Claims. (61. 114-152) This invention relates towatercraft and more particularly is concerned with means of steeringwatercraft by controlled banking.

While I address my specification particularly to high speed watercraft,it will be clear that my invention applies equally advantageously toslower craft.

It is well known that with watercraft of conventional design employing arudder, the rudder merely points the craft in the desired direction byinducing a yaw. This does not necessarily set it on course. The reasonfor this is that no body is controlled in its course by merely changingits orientation. It is only by the application of a lateral(centripetal) force that the course of body is altered. While it isgenerally true that the rudder finally accomplishes the effect ofsteering the watercraft, actually this is accomplished by a complicatedchain of loosely related events of which the production of centripetalforce and the turn are the last and these are byproducts of the originalyaw. Since the side forces (centripetal) produced in this manner arealways associated with yaw, actually the watercraft is in a skid when itis turned by means of a rudder. This is particularly unde sirable if thewatercraft is travelling at high speed. When travelling at high speed, acraft that begins to skid or is put into a skid deliberately by theoperator is at the mercy of the slightest untoward incident. It can bethrown out of control by any sudden irregularity of the hydrodynamicpattern such as by hitting a swell, or by entering into a trough. Itfollows that the rudder is usable for correcting or introducing yaw andthus steering a watercraft at reduced speed but, as set forth above, forhigh speed watercraft the ordinary rudder is whollyinadequate as thebasic steering device. For the same reasons steering by pivoting anoutboard motor is also inadequate.

It will be seen that my invention is equally applicable to watercraftthat are propelled by waterscrews, by airscrews, by jets, as well as byany other means. Accordingly, the propulsion system of the watercraftwill be largely disregarded in this specification.

High speed watercraft are subject to considerable dynamic forces whichto greater or lesser extent supplant static buoyancy and which thusforce the hull, entirely or partly, out of the water.

My method of watercraft steering takes advantage of these forces and isas follows: I cause those components of the watercraft which producedynamic sustentation forces to bank to a degree deliberately selectedand accurately controlled by the operator. This correspondingly tiltsthe above dynamic forces. Their horizontal components produce thecentripetal effect responsible for the turn. Thus, I radically differfrom the present rudder controlledor outboard motorcontrolled-watercraft. Whereas the latter are yawed for the purpose ofturning, I cause my watercraft, or certain appropriate componentsthereof, to tilt laterally. In other words, instead of rotating mywatercraft about a vertical axis, as is usually done, I tilt it (or itscomponents) about a longitudinal axis (or axes). It is true that uponapplication of the rudder, some of the rudder controlled watercraft tendto heel. However, the operator does not directly control the angle ofbank, but must accept it as it comes with the yaw. Watercraft which aresteered on their course primarily by yaw controlling devices are ofnecessity limited in their maneuverability. The teachings 3,124,096Patented Mar. 10, 1964 of the invention suppress the objectionableskidding. Sailboats are also known to heel sharply. However, the heelingof a sailboat is not of the same nature as the controlled bankingeffected by my invention, and in their effects they are not comparable.

One of the greatest dangers in high speed watercraft operation is thematter briefly touched upon above, where skidding associated withturning can throw the watercraft out of control. Because of this danger,high speed watercraft are constitutionally not adapted for sharp turns;they must either be slowed down for change of direction are negotatiatewider turns. By providing a more rational and scientific method ofturning, in accordance with the teachings of this invention, themaneuverability is considerably improved. The means which I use alsoimproves lateral stability. Thus, as will be seen from the followingspecification, one of the advantages of my invention is to reconcile thegenerally conflicting requirements of lateral stability andmaneuverability.

It will be apparent from the following specification that my inventionis applicable to watercraft of any designs, that is to hulls that runpartly in immersed condition, as well as to hulls that hydroplane on thewater surface, and also to high speed watercraft that are lifted clearout of the water by means of hydrofoils, or any other dynamic liftingdevices.

It is the principal object of my invention to provide a method ofsteering watercraft by inducing a strictly controlled bank of said craftduring its movement.

It is a further object of my invention to provide watercraft withinherent lateral stability both in straightaway and in turns.

It is a still further object of my invention to provide a means forsteering a high speed watercraft that does not primarily produce yaw. Asused herein and in the claims, the terms yaw, yawing angle, etc. referto such rotations (or angles associated therewith) of the craft aboutits vertical axis, whereby the centerline of the craft is unaligned, oris brought out of alignment with the tangent to its course relative tothe water.

In summary, the nature of my invention is to provide a method ofdirectional control of high speed watercraft by use of means for strictcontrol of the angle of bank and by stabilizing the craft at theselected angle of bank.

This specification refers to several examples of watercraft which bankbodily, retaining their permanent shape. In other examples, alsodisclosed in this specification, the craft banks not as a solid unit,but modifies its geometric shape as those elements which produce dynamicsupport, bank. In still other examples, some of the components of thecraft which are not involved in the generation of the dynamicsustentation forces, do not participate in the banking at all.Regardless of these secondary distinctions, all the above Watercraft canbe described in a broad sense as being banked in a turn. As employedabove, and hereinafter in the specification and claims, the terms bankand tilt are broadly used to refer to the banked condition of theWatercraft (or its support elements).

All of the foregoing and further objects of the invention may be morereadily understood by a reading of the description followinghereinafter, having reference to the appended drawings.

It will be clearly understood that the scope of my invention is notlimited to these drawings but that the drawings are submitted merely asillustrative examples of my invention. For convenience I have employedschematic figures showing the essentials of my invention from which Ihave omitted nonessential details. In the drawings:

FIGURE 1 is a schematic drawing showing a side view of a watercraftembodying my invention equipped with lateral bank regulating hydrofoils;

FIGURE 2 is a front view schematically illustrating this form of myinvention;

FIGURE 3 is a perspective view illustating details of the control meansof the watercraft shown in FIGURE 1;

FIGURE 4 is a diagrammatic illustration of a servocontrol;

FIGURE 5 is a schematic illustration of a watercraft showing theposition of my hydrofoils employing a positive angle of attack;

FIGURE 6 is a plan view of a modification of a por tion of the controlmeans of FIGURE 3;

FIGURE 7 is a schematic side elevation of another form of my invention;

FIGURE 8 is a schematic front View of FIGURE 7;

FIGURE 9 is a schematic view showing a detail of a means of controlemployed in FIGURE 8;

FIGURE 10 is a side view of another form of the invention;

FIGURE 11 is a rear view of the watercraft shown in FIGURE 10;

FIGURE 12 is a view similar to FIGURE 11, but showing the watercraft ina banked condition;

FIGURE 13 is an enlarged rear view showing the area A of FIGURE 11;

FIGURE 14 is a cross-sectional view taken along line 14-14 of FIGURE 12;

FIGURE 15 is a side view of another form of my invention provided withan aerodynamic servo-control system;

FIGURE 16 is a schematic representation of the servocontrol systememployed in FIGURE 15;

FIGURE 17 is a side view showing a portion of an aerodynamicservo-control alternate to that shown in FIGURE 15;

FIGURE 18 is a side elevation of another form of the invention;

FIGURE 19 is a front view of the watercraft shown in FIGURE 18.

Similar numerals refer to similar parts throughout the entirespecification.

All watercraft shown in the above figures are of essentially symmetricdesign, though some deviations from strict symmetry may be required forthe purpose of correcting an imbalance associated inherently with theoperation of the craft (for example, the unbalancing effect produced bypropeller torque). In my specification and drawings I discount suchunbalancing effects and the associated corrective features; for allpractical purposes, the watercraft described in this specification aresymmetric. However, my invention is not limited to symmetricallydesigned watercraft, and it is intended to be applicable to assymmetricwatercraft.

Keeping in mind that one of the basic principles of my invention is tosteer a fast moving watercraft by causing it to bank in a controlledcondition, I refer to the drawings in which I show in FIGURES 1 and 2 aconventional hydroplane hull 1 having two steps B and B and a fin orrudder C. (For the purposes of this specification, I make nodistinctionunless otherwise stated-between a fin fixedly attached to thehull, and a steerable fin rotatively mounted about a substantiallyvertical axis, i.e. a rudder.) My watercraft employs such a fin orrudder only to insure directional stability and for production of yawmoments and control of the yaw angle. I do not use the rudder as aprimary steering device, except in an auxiliary capacity, for example,at speed below operational, when the method of steering described inthis specification becomes inefiicient due to greatly reduced dynamicforces. I mount hydrofoils 2 and 3 on arms 4 and 5, which are hinged asat 6 and 7, respectively (as shown in FIG. 3), to the supports 8 and 9,which in turn are fastened to the hull 1. The hydrofoils 2 and 3 can berotated about the hinges 6 and 7, respectively, or retained in any givenposition, as described hereinafter. In FIG. 2 they are shown in theirneutral condition, i.e. symmetric with respect to hull 1, and extendingto or penetrating below the waterlevel. The position of the hydrofoils 2and 3 is such that the hydrodynamic forces developed by the immersedportion thereof follow a line passing below the crafts center ofgravity. The hydrofoils 2 and 3 are established at positive angles ofattack. The angle of attack is positive when it produces hydrodynamicforces f and f which are outwardly acting as shown in FIGURE 5.

The function of hydrofoils 2 and 3 is to stabilize the watercraft at anydesired angle of bank selected within design limits. Thus the craft issteered on its course and the hydrofoils provide automatic stability ofthe selected bank angle. It is indeed clear, when the craft is in theposition shown in FIGURE 2, i.e. the hull I is not banked and thehydrofoils 2 and 3 are undefiected from their neutral, symmetricarrangement and penetrate to an equal depth into the water, that theforces and 3 are equal, act symmetrically, and produce no rolling momentupon the craft. Should, however, the depth of penetration of thehydrofoils become unequaleither consequent to a bank of the hull 1, orbecause of a differential or uneven rotation of the hydrofoils 2 and 3about their respective hinges 6 and 7, or because of a combination ofthe above conditions-the moments produced by forces f and f would notbalance each other. Considering the direction of the forces f and f andthe location of the crafts center of gravity with respect to theseforces as defined previously, it is clear that the resultant rollingmoment rotates the craft in that direction which tends to restore thehydrofoils 2 and 3 to equal immersion. Thus, when, due to some outsidecause, the hull 1 becomes tilted, the hydrofoil system responds byproducing a rightening moment, which in case of a passing disturbancerestores the hull back to normal, and in case of a permanent cause (forexample, the shift of the center of gravity) arrests further tilt aftera small angle of bank has been reached. On the other hand, if and when,with the hull normal, the hydrofoils 2 and 3 are differentially, i.e.unevenly, rotated about their respective hinges 6 and 7, their relativeimmersion becomes unequal. This brings into existence a rolling momentcreated by the manipulation of the hydrofoils; the hull 1 is bankeduntil the hydrofoils 2 and 3 have reached a position of equal immersionand the forces 1; and f become balanced, at which angle of bank thecraft again reverts to lateral equilibrium. The angle of bank is thusstrictly determined by the position of the hydrofoils 2 and 3 abouttheir hinges 6 and 7. This position depends solely on the operator whothereby is in complete control of the angle of bank.

Therefore, the bank angle is determined solely by the degree ofdeflection of the hydrofoils from their neutral position, i.e. abouthinges 6 and 7. This contrasts with the behavior of other craft whoseangle of bank is controlled by the operation of ailerons or similardevices. In the case of such craft, the position of the aileronsdetermines the rate of roll, and not the angle of bank. The operator ofthese craft, after having initiated a rolling moment, must also activelyarrest it. He also must continuously monitor his controls, for theailerons do not provide stability about the roll axis. Hydrofoils havebeen known to be used for the purpose of securing lift to watercrafthulls that rise above water. It is also known to employ hydrofoilsattached to the hulls of scaplanes for the purpose of assisting thecraft in take-off. However, prior to my invention, it has not been knownto arrange and operate hydrofoils in the manner set forth in thisspecification and to employ them for the purposes herein set forth.

As one means of hydrofoil control of the craft of FIGS. 1-3, a platform14 is provided, upon which the operator of the watercraft may stand. Theplatform 14 is mounted on an axle 15 supported in bearings 15'substantially as shown. A suitable handlebar 17 is mounted in front of Ihave shown in FIG-' attached to the platform 14 and the arm 4. Anothercable 19 is symmetrically attached to the right side of platform 14 andthe arm 5. The platform 14 may be tilted to starboard or port by mereshift of the weight of the operator. When tilted in the direction shownby the arrow G, it will press the hydrofoil 3 downwardly while hydrofoil2 will move upwardly (see arrow H) under the compulsion of thehydrodynamic force h. It will be apparent that an operator standing onthe platform 14 and depressing the latter on one side or the other willmove one hydrofoil in and the other out of the water. He can steadyhimself by gripping the handle bar 17. The platform 14 may be soconstructed and arranged that the centering springs 16 and 16' urge theplatform to a neutral or normal position.

It is clear that the degree of lateral stability depends on themovements of platform 14 about the hinge 15. Thus, if the platform isrestrained from rotating about the hinge (in other words, if it issteadied with reference to the hull), the hydrofoils 2 and 3 exercise astabilizing effect on the hull. This effect can be reduced and evenreversed if, as the craft banks, the platform is given an additionaltilt in the same direction. Conversely, the stabilization can beaugmented by tilting the platform in a direction opposite to that of thebank.

As to the directional control through controlled banking, such controlis achieved by tilting the platform 14 to one side or the other, as isclear considering the efiect of the hydrofoils on the banking attitudeof the watercraft.

The control system may be arranged for operation from a seated ratherthan a standing position. In this case, a rudder bar 14', hinged about avertical axis, can be employed as shown in FIGURE 6. The kinematics ofthe arrangements shown in FIGURES 3 and 6 are the same and thecorresponding components are in the same relation.

Of course, if desired, instead of having a foot operated control such asplatform 14-, or rudder bar 14', the hydrofoils 2 and 3 may be linked toa manually operated control, for example, a control wheel, stick, etc.without departing from the spirit of my invention.

It is also clear that the number of hydrofoils on each side of the hullneed not be limited to just one, as shown in FIGURE 1. There may be asmany hydrofoils as desired, their effects on stability and control beingadditive.

The above control requires that the craft be restrained from yawing. Yawalters the angle of attack of the hydrofoils, reduces lift on one side,increases it on the other, which leads to a rolling moment and abanking. Consequently, the craft requires close yaw control, orpreferably, requires good inherent directional stability. The latter isachieved through use of a powerful vertical tail fin (or rudder) C. Thefin C should be preferably be operated in water, as shown in FIGURE 1.An aerial fin would be affected by the wind and would induce a yaw ofits own. Nevertheless, an aerodynamic fin is not necessarilyobjectionable, if appropriate means are provided for properly trimmingit out. My hydrofoil system, if associated with satisfactory directionalstabilization is sufiicient for directional control and requires norudder. However, the fin C may be hinged about a vertical axis andoperated as a rudder for more delicate yaw regulation or other auxiliarypurposes and for steering at low speeds. The rudder C may be steered byhandlebar 17, which, in that case, is rotatably mounted and can turnlike a bicycle handlebar. A steering wheel with proper linkage, in lieuof the bar, is another convenient arrangement.

During the time that the operator maintains the platform 14 steady atthe selected tilt, the platform 14 may be rendered self-locking in anydesired position established by the pilot. In this latter case the craftwill stabilize itself at any angle of bank established by the choice ofthe pilot. Such self-locking feature may be achieved by merely renderingthe control system irreversible such as is known in the steering ofvarious vehicles, for example, aircraft. Irreversible controls includingservo-controls and boost mechanisms are within the state of the art andrequire no description here. However, one novel form of such boostcontrol arrangement is shown in FIGURE 4. This arrangement converts thecontrol system illustrated in FIGURE 3 into an irreversible boostmechanism. Referring to only one side of the control system since bothoperate similarly, the pilots command is transmitted from platform 14-through the cable lii' to hydrofoil 2. Only a portion of the cable It)is represented in FIGURE 4 together with the arrangement that has beenadded for servo-operation. All other components are the same as thoseshown on FIG- URE 3. On its way from platform 14 to hydrofoil 2, thecable 10' is wound around a drum 21 in an arc that can measure from afraction of a complete winding to as many turns as desired. The drum 21is power driven, as for example, by an electric motor and iscontinuously rotating in the direction shown by the arrow b When tensionexists on both ends of the control cable 10' (as indicated by b and bthe coil around the drum 21 clutches it tightly and the ensuing frictioncauses the cable lit to follow the drum 21 overcoming the resistance 12Thus it inserts the hydrofoil 2 deeper into the water. Tension b, isproduced by the pilot as he tilts the platform 14. When the pilotslackens the cable by reversing his action, the hydrofoil 2 uses thereleased length of the cable 10' to rise (totally or partially as thecase may be) out of the water. The described boost system utilizes thetorque of the drum 21 to relieve the strain on the pilot and overcomethe hydrodynamic forces that act on the hydrofoils 2 and 3 which producethe cable tension [2 Only a very weak force b is required to balance outb Referring to FIGURE 5, I have illustrated the effect on directionalstability of the location of my hydrofoils shown in FIGURES 1 and 2. Ihave schematically shown in FIGURE 5 the horizontal projection of thehydrofoil generated forces and have designated them respectively f and fThey intersect at point a which is normally contained in the plane ofsymmetry of the craft and is only slightly displaced therefrom by theoperation of hydrofoils 2 and 3. The effects of this displacement aresmall in the arrangement shown and will be temporarily ignored for thepurposes of discussion. The resultant of f and f moves in and out of theplane of symmetry of the craft depending upon the variations of therelative magnitudes of f and 3. If f equals f their resultant iscontained in the plane of symmetry of the craft which also contains thecenter of gravity a. Hence the resultant produces no yawing moment. Whenf and f become unequal, their resultant has a transverse component, itproduces a yawing moment proportional to the horizontal distmice betweenpoint a and the center of gravity a of the craft. Consequently, thepreferred location of the hydrofoil system would be that whichestablishes point a substantially on the crafts vertical axis passingthrough its center of gravity. However, small deviations from the abovedescribed position of point A are desirable to take into account theWandering of point A in and out of the plane of symmetry and, also todeliberately create a yawing moment by foils 2 and 3 to counteract in abank such yawing moments, which may arise (depending on the specificcharacteristics of the particular design) in consequence of forces otherthan those produced by hydrofoils 2 and 3.

As shown in FIGURE 7, I have schematically repre sented a hydrofoil boatof the so-called Hydrodyne type which I now equip for lateralstabilization and directional control with my hydrofoil system. In thistype of watercraft, the weight of the Hydrodyne is supported by thelifts generated by the ski 5i and hydrofoil 5]..

This configuration exhibits excellent longitudinal stability andseaworthiness. FIGURE 13 is a front view of FIGURE 7 and shows thehydrofoils 2 and 3 rotatably mounted about transverse axis line AA tothe hull 1 and oriented downwardly substantially as shown. In this formof my invention, the hydrofoils 2 and 3 assume a considerable sweepforward when in neutral position. The hydrofoils 2 and 3 arerotationally mounted on bearings 54 and 56 and the up-and-down movementof hydrofoils 2 and 3 relative to each other is achieved by rotating thehydrofoils differentially about the axis line AA so that one bitesdeeper into the water while the other is retracted. This produces arolling moment which banks the Watercraft.

As shown in FIGURE 8, the hydrofoils 2 and 3 not only project downwardlybut also outwardly, thus increasing the effectiveness of the hydrofoilsystem as compared to the arrangement shown in FIGURE 1. As establishedin the foregoing description, the directional control is achievedthrough differential variation of the immersed hydrofoil areas. If it isdesired to steer the craft to port, it will be possible to induce thecraft to bank to port by immersing the starboard hydrofoil deeper intothe water and retracting the port hydrofoil correspondingly. Then, forthe duration of the turn, the hydrofoils are maintained in theconfiguration corresponding to the appropriate angle of bank. After theturn has been accomplished, the hydrofoils are returned to neutralposition.

In FIGURE 9 I have shown a simple arrangement for differential controlof the hydrofoils 2 and 3. By means of a steering wheel and transmission(not shown) the pilot operates a bevel gear 58. The bevel gear 58 is inmesh with bevel gears 69 and 62 which are respectively assembled withthe hydrofoils 2 and 3 by means of connecting shafts 64 and 66. Thuswhen the bevel gear 58 is rotated, the hydrofoils 2 and 3 turn inopposite directions.

Referring to FIGURES 10, 11 and 12, the invention is shown in the formof a watercraft supported by multiple lifting elements so kinematicallylinked together that the geometry of the craft can be changed at will bythe operator. As this is done, the lifting elements are re-orientedvertically with respect to each other and assume from port to starboardan ascending, or descending (as the case may be), stairway pattern. Inthe foregoing, vertical, ascending, and descending refer to directionsestablished in a system of coordinates bound to a conveniently selectedelement of the watercraft itself, for example, the hull. The kinematicconnections are preferably such that the lifting elements shift substantially parallel to themselves with such exceptions as will be shownlater.

It will be clear that above a certain speed the hydroplane shown inFIGURES and 11 rises to the surface and glides at water level. Thehydrodynamic lift is applied to the bottom of the floats 2 and 3 and tothe step B on the bottom of the hull 1. As shown in FIG- URE 11, thefloats 2 and 3 are attached respectively to the struts 68 and 71). Thestruts 68 and 70, and hence the floats 2 and 3, are linked together bymeans of two parallel beams 72 and 74, and hinges 76, 78, 3t) and 82,substantially as shown. This assembly constitutes a four-link kinematicchain. The beams 72 and 74 are articulated to the hull 1 at theirmidpoints 84 and 86 by hinges 88 and 9t). The kinematic chain formed bylinks 63, 70, 72 and '74 may be actuated by an appropriate controlsystem. One such system is shown in FIGURES 13 and 14. The beam 74 and aspindle 92 are held together by means of a key 94. Another key 93retains a horn 96 on the spindle 92. The latter is rotatively mounted ina bearing 1% in hull 1. Cables 102 and 194 pass over pulleys 106 and108, and connect the horn 96 with the control Wheel (not shown). Bymeans of the cables 102 and 104, the operator can exercise a lateralforce on the horn 96, as desired. This will result in impressing atorque on the beam 74. The horn 96 cannot be moved away from the truevertical since its position is controlled by floats 2 and 3 which,together with the hull 1, rest on the horizontal surface of the water.Consequently, the force which tends to move the horn 96 laterally willreact on the hull 1 and actually result in banking the hull 1 and thefloats 2 and 3 by deflecting the quadrilateral 68, 72, 70 and 74, asshown in FIGURE 12. When the gliding surfaces become tilted, as shown inFIGURE 12, the effect is to bank the hydrodynamic lift forces away fromthe vertical, and to give them a horizontal transverse component. Thehydrodynamic lift forces are thus banked to an angle strictly defined bythe deflection of the operators controls and the consequent translationof cables 102 and 164, as is desired in order to obtain the centripetalforce required to cause the craft to turn.

Owing to the fact that the kinematic chain formed by links 68, 70, 72and 74 is a parallelogram articulated to the hull 1 at the midpoints oflinks 72 and 74, the deflection of this chain produces equal tilt of alllifting elements (i.e. of hull 1 and floats 2 and 3). Consequently, thedynamic lift forces generated by these elements are tilted by the sameangle and compose into a resultant force and no couple. Since, as wasassumed, the sustentation force produced by these elements in astraightaway (i.e. when the craft is not tilted) passes through thecenter of gravity, banking produces no yawing moment. If, on the otherhand, the resultant sustentation force was acting in front or in therear of the center of gravity (as can sometimes occur, for example, whenthe craft is subjected to a pitching moment produced by thrust whichdoes not act through the center of gravity), then a mechanism such asdescribed would produce a yawing moment when banked. In that case, itmight be desirable to compensate for this moment by intentionallycreating a yawing couple. One of the means to achieve this is to departfrom the parallelogram geometry of the kinematic chain. Such anarrangement, which by its geometry must be related to and madeconsistent with the yawing moment to be compensated for, is illustratedon FIGURE 19.

Because the tilting of the craft as explained above is achieved byphysical effort, the requirement may arise for servo-control or boostmechanisms. These are of such standard design that it is not considerednecessary to describe any particular form. However, for illustrativepurposes FIGURES 15 and 16 show a novel servomechanism which has beenfound useful. Referring to FIGURE 15, a vertical aerial fin 112, of thefree-floating type, is mounted on a mast 110. The fin 112 carries acontrol tab 114' and is rotatably mounted on a vertical axis 114 whichis located in front of the fins center of pressure. With suchqualifications as has been discussed above, it is preferable that theaxis 114 be located in close proximity to the vertical axis of inertiaof the craft to prevent the appearance of a substantial yawing momentwhich otherwise would be produced by the operation of the fin 112. Theoperation of this arrangement may be explained as follows: Referring toFIGURE 16, an epicyclic train (or difierential) 116 is carried inbearing 117 in the hull. The pinion 120 is rotationally controlled bythe operator. The pinion 122 is keyed to the cross-bar 74 which isattached to the floats 2 and 3. Since the floats 2 and 3 are always incontact with the water, the pinion 122 does not actually rotate withrespect to earth coordinates, but it can rotate with respect to thehull 1. The chassis 118 of the differential 116 is connected by gears,cables or by any other suitable means, to the control tab 114. When thehull 1 banks for any reason, the pinion 122 rotates with respect to thehull. Assuming the pinion 121) is not rotated by the operator, thiscauses the chassis 118 to correspondingly rotate, resulting in the tab114' being deflected. The fin 112 is thereby also caused to deflect.Such deflection generates an aerodynamic force which produces arightening rolling moment.

On the other hand, if the operator desires to cause the craft to turn,he introduces a rotating movement in the pinion 120, causing the chassis118 to turn and to activate the fin 112 which produces the desired bank.

The only forces which are feeding into the control system originate fromthe resistance to the operation of control tab 114' and since they aresmall, irreversible controls are not generally required.

FIGURE 17 shows a modification of the control system illustrated inFIGURES l and 16. The epicyclic train is eliminated. Instead of theepicyclic train 116, the fin 112 is provided (see FIGURE 17) with twoindependent control tabs 114' and 115. The control tab 114' is linkeddirectly to the operators control, while the control tab 115 is linkeddirectly to the horn 96, as shown in FIGURE 13. The tab 114 controlledby the operator is designed so as to always prevail. The floats 2 and 3can be provided with a device to lock them at rest in a position ofsymmetry shown in FIGURE 11.

In the type of craft shown in FIGURE 11, the floats 2 and 3 can bereplaced by water skis provided the hull offers adequate staticbuoyancy.

The craft shown in FIGURE is supported by three lifting surfacesarranged in an isosceles triangular pattern with the apex of thetriangle in the forward position. This arrangement could be reversed toestablish the apex in the rear of the craft, if desired. The floats orskis 2 and 3 are then moved forward and the step B is moved to the rear,as shown in FIGURE 18.

The three point suspension could also be replaced by a four pointsuspension similar to that of a four wheel vehicle. In this case, thehull 1, or any substitute thereof, need not be in contact with thewater. If it is, the craft assumes a five point suspensionconfiguration. In fact, the number of lifting surfaces can be furtherincreased if desired. In the case of four point suspension the liftingelements may be in the shape of four separate pontoons or of two long,parallel, side-by-side floats each gliding on two steps. In the case offour or more point suspension, with the lateral elements providingstatic buoyancy as well as dynamic lift, the body of the craft (hull 1of FIGURE 10) may be simplified. It may assume the shape of a platformor any other desired shape. In the alternate case, the central body mustprovide static buoyancy, i.e., it may be in the shape of a hollow hull,a raft-like structure, or any other convenient shape. In thisalternative case, the hydrodynamic support is divided among four skis.The latter may or may not be rigidly interconnected in pairs.

The mechanical connections disclosed in FIGURE 11 are only a sample ofthe various mechanisms that may be employed to accomplish theconfiguration of variable geometry as defined above. When the centralbody, or hull 1, does not participate in the dynamic lift of thewatercraft, it is not always essential, from an operational point ofview, whether the hull 1 does or does not bank in a turn. However, forthe comfort of the passengers, it may be preferable that the hull 1 bebanked.

Referring now to FIGURES 18 and 19, the skis 2 and 3 serve assubstitutes for the lateral floats 2 and 3 of FIGURE 11. It will be seenthat the skis are in front of the craft and the step B of the hull 1 isin the rear. The skis 2 and 3 are hinged to the hull 1 by means of twoseparate four-bar kinematic chains formed respectively at thequadrilateral hinges 126, 128, 130 and 132; and 134, 136, 138 and 140.The control system is represented by cables 144 and 146 which run fromthe respective ski assembly over pulleys 148 and 150 to the operator.The two kinematic chains are also joined by means of a tension cable142. The tension cable 142 is intended to relieve the load which,otherwise,

would be fed into the control system. Thus, a means is provided for theport and starboard lift forces to substantially balance each other. Thecables 144 and 146 transmit into the control system only, thedifferential forces produced by occasional unbalance between thehydrodynamic lift forces developed by the skis 2 and 3. The same effectis achieved in the configuration shown in FIGURES 10 and 15.

Unlike in the watercraft of FIGURES 10 and 15, the guiding surfaces ofthe craft 23, 24 change their angular relationship on deflection fromneutral position. This is due to the fact that the quadrilaterals 126,128, 130, 132 and 134, 136, 138, are not parallelograms, in contrast tothe kinematic chains of the cited figures. Such an arrangement producesa yawing couple when the craft is banked. It is shown to illustrate thecase of a craft in which banking is coupled with a yawing momentconsequent to the presence of such forces as aerodynamic pressures,propeller traction etc. The yawing couple induced by the geometry of thedeformed kinematic chains 126, 128, 130, 132 and 134, 136, 138, 140serves to counteract the above yawing moment. Thus, by properlyproportioning the links of said chains, it is possible to correct orreduce the yawing effects traceable to the presence of forces other thangravity.

Having described my invention what I regard as new and desire to protectby Letters Patent is:

1. In a watercraft of the character described, at least one hydrofoilmounted on port and one hydrofoil mounted on starboard of saidwatercraft, said hydrofoils movably mounted in a manner which permitslowering and raising of said hydrofoils, said hydrofoils being orienteddownwardly and normally mounted at least partially out of the water,each hydrofoil adapted to generate, when immersed to any extent,outwardly directed hydrodynamic lift forces, said lift forces followinga line of action passing below the center of gravity of said watercraft,means in said watercraft responsive to control activation and operablyconnected to said hydrofoils, said last means adapted to movedifferentially said hydrofoils in said manner, thereby producing aresultant rolling moment causing said watercraft to assume a bank at theangle determined by said control activation.

2. In a surface watercraft, means providing sustentation to thewatercraft during run by generating dynamic forces which substantiallybalance the weight of the watercraft; operable hydrofoil means on eachside of the watercraft adapted to generate controllable dynamic forcesacting substantially laterally and varying in magnitude as thewatercraft banks thereby producing concomitant rolling moments to rotatethe watercraft to the selected angle of bank and inherently stabilize itlaterally at said selected bank angle and steering controls operativelyconnected to said hydrofoil means.

3. The watercraft of claim 2 wherein said sustentation means areseparate and independent from said operable hydrofoil means.

4. In a surface watercraft, means providing sustentation to saidwatercraft during run by generating dynamic forces which substantiallybalance the weight of said watercraft; operable means to rotate saidwatercraft during run to the selected angle of bank and to inherentlystabilize it at said angle of bank, said operable means comprisingdownwardly oriented hydrofoils mounted on the port and starboard sidesof the watercraft so that normally during run at least a substantialpart of the hydrofoil remains out of the water, said hydrofoils beingestablished at angles such as to generate when immersed to any extentcontrollable hydrodynamic forces acting substantially laterally andproducing concomitant rolling moments acting in that direction whichurges the watercraft to rotate away from the hydrofoil generating saidforce and moment; steering controls being operably connected to saidport and starboard hydrofoils so that operation of the hydrofoilsproduces differential variations in said port and starboard hydrodynamicforces and rolling moments.

5. The watercraft defined in claim 4 wherein the sustentation means areseparate and distinct from said operable hydrofoil means.

6. In the watercraft of claim 4, mounting means for said port andstarboard hydrofoils, arranged so as to permit said hydrofoils to bemovable by said steering controls up and down relative to one another.

7. In the watercraft of claim 6, said hydrofoils being rotatably mountedabout axes substantially parallel to the longitudinal axis of saidwatercraft.

8. In the watercraft of claim 6, said hydrofoils being rotatably mountedabout axes substantially parallel to the transverse axis of saidwatercraft.

9. The watercraft defined in claim 6 including a plurality of cables insaid Watercraft responsive to control activation and operably connectedto said hydrofoils, each of said cables being wound around a drum powerdriven in a constant direction, each of said cables adapted to betightened around said drum when the respective hydrofoil is to be movedin a direction compatible with the direction of the drums rotation andto be loosened when said hydrofoil is not to be moved in a directioncompatible with the direction of the drums rotation, said cables adaptedto move differentially said hydrofoils in said manner, thereby producinga resultant rolling moment causing said watercraft to assume a bank atthe angle determined by said control activation.

10. In the watercraft of claim 2, said operable hydrofoil means being solocated in relationship to the center of gravity of said watercraft asto produce hydrodynamic forces whose lines of action run at suchdistance and in such relationship to the center of gravity as to composeinto a resultant producing no adverse yawing moment.

11. In the watercraft of claim 2, vertical tail means operating inwater.

12. In the watercraft of claim 4, said hydrofoils being established insubstantially vertical planes.

13. In the watercraft of claim 4, said hydrofoils being established inplanes inclined on the vertical and substantially parallel to thelongitudinal axis of said watercraft, said planes converging abovewater.

References Cited in the file of this patent UNITED STATES PATENTS1,112,405 Forlanini Sept. 29, 1914 1,186,816 Meacham June 13, 19161,410,876 Bell et al Mar. 28, 1922 1,846,602 Lake Feb. 23, 19321,888,107 Batt Nov. 15, 1932 2,347,959 Moore et al. May 2, 19442,584,347 Hazard Feb. 5, 1952 2,749,871 Scherer et a1. June 12, 19562,795,202 Hook June 11, 1957 2,848,971 Kollenberger Aug. 26, 1958FOREIGN PATENTS 100,275 Austria Jan. 15, 1925

1. IN A WATERCRAFT OF THE CHARACTER DESCRIBED, AT LEAST ONE HYDROFOILMOUNTED ON PORT AND ONE HYDROFOIL MOUNTED ON STARBOARD OF SAIDWATERCRAFT, SAID HYDROFOILS MOVABLY MOUNTED IN A MANNER WHICH PERMITSLOWERING AND RAISING OF SAID HYDROFOILS, SAID HYDROFOILS BEING ORIENTEDDOWNWARDLY AND NORMALLY MOUNTED AT LEAST PARTIALLY OUT OF THE WATER,EACH HYDROFOIL ADAPTED TO GENERATE, WHEN IMMERSED TO ANY EXTENT,OUTWARDLY DIRECTED HYDRODYNAMIC LIFT FORCES, SAID LIFT FORCES FOLLOWINGA LINE OF ACTION PASSING BELOW THE CENTER OF GRAVITY OF SAID WATERCRAFT,MEANS IN SAID WATERCRAFT RESPONSIVE TO CONTROL ACTIVATION AND OPERABLYCONNECTED TO SAID HYDROFOILS, SAID LAST MEANS ADAPTED TO MOVEDIFFERENTIALLY SAID HYDROFOILS IN SAID MANNER, THEREBY PRODUCING ARESULTANT ROLLING MOMENT CAUSING SAID WATERCRAFT TO ASSUME A BANK AT THEANGLE DETERMINED BY SAID CONTROL ACTIVATION.